The present invention relates to electrostatographic reproduction machines for producing sets of document copy sheets, and more particularly to a universal and precise stapling method and apparatus for stapling such sets of document copy sheets despite stack-up tolerances of stapling assembly components.
In a typical electrostatographic reproduction machine or toner image reproduction machine, portions of a rotatable photoconductive member in the form of a drum or a belt, are charged sequentially to a substantially uniform potential so as to sensitize the surface thereof. The charged portions of the photoconductive member are exposed to a light image of an original document being reproduced. Exposure of the charged photoconductive member thus selectively dissipates the charges thereon in the exposed areas. Such exposure forms an electrostatic latent image on the photoconductive member that corresponds to the informational areas contained within an original document to be reproduced.
After the electrostatic latent image is formed on the photoconductive member, the latent image is developed by bringing a developer material into contact therewith. Generally, the developer material comprises toner particles adhering triboelectrically to carrier granules. The toner particles are attracted from the carrier granules to the latent image forming a toner powder image on the photoconductive member. The toner image is then transferred from the photoconductive member to a copy sheet of paper where the toner particles forming the toner image are heated to permanently affix the toner image to the copy sheet forming a copy of the original image.
A mass of copies of the original image can be formed in this manner. Other copy forming machines of course include printing presses, and the like. With the advent of higher speed and more sophisticated copy producing machines, such as electrostatographic reproduction machines and printing presses, one way of handling such copies has been to provide a finishing device or finisher that includes a stapling assembly that organizes the copies into sets, and binds or staples them. In such a finisher, the copies or copy sheets are collected in collated sets as they are sequentially produced by the machine for binding by a stapling head of the stapling assembly without the interaction of additional devices.
The stapling assembly of such a finisher usually includes a copy sheet alignment apparatus, a moveable stapling head and means for moving the stapling head. The alignment apparatus can be one of two types, namely an edge-alignment type, or a center-alignment type. The stapling head is ordinarily moved back and forth relative to an aligned set of sheet in a cross-process direction and to various positions within the stapling assembly for locating staples, and performing stapling operations, on an aligned set of copy sheets.
The accuracy of the locations of staples from any edge of the aligned set copy is dependent on many factors including the assembly tolerance stack-up of the relevant parts and components of the alignment apparatus and the stapling head. Usually, the staples are specified to be located at predetermined distances from the edge of the aligned set of sheets. However, because of the design tolerances on individual parts and components of the alignment apparatus and the stapling head, the tolerances as well as the stack-up of such tolerances, the actual staple locations achieved can vary significantly from specified locations. The undesirable results can include staples missing some edges partially or completely. This problem is aggravated when a stapling head initially set for an edge-alignment apparatus is used with a center-alignment apparatus.
Conventionally, attempts to avoid such undesirable results and to achieve much more precise location of staples on aligned sets of sheets by mechanical means have typically involved trying to design all the parts and components to tighter and tighter tolerances. This of course is not desirable because it results in relatively more costly and stringent manufacturing control of such parts and components, as well as in much higher cost of manufacturing.
In accordance with the present invention, there is provided a universal and precise stapling assembly including (a) a moveable stapling head for driving staples at precise locations through an aligned set of sheets on any one of a plural types of alignment apparatus; (b) a drive means coupled to the stapling head for moving the stapling head relative to the any one of plural types of alignment apparatus and the aligned set of aligned sheets on the any one of the plural types of alignment apparatus; (c) sensor means for sensing a position of the aligned set of sheets; and (d) a programmable controller connected to the drive means, to the sensor means, and to the stapling head, and including calculating means for precisely calculating a precise staple location responsively to a type of any one of the plural types of alignment apparatus and to the secured position of the aligned set of sheets, thereby reducing staple mislocation due to a tolerance stack up from components of the stapling head and of any one of the plural types of alignment apparatus.